/*
 * FreeRTOS Modbus Libary: A Modbus serial implementation for FreeRTOS
 * Copyright (C) 2006 Christian Walter <wolti@sil.at>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */



/* ----------------------- System includes ----------------------------------*/
#include "stdlib.h"
#include "string.h"

/* ----------------------- Platform includes --------------------------------*/
#include "port.h"

/* ----------------------- Modbus includes ----------------------------------*/
#include "mb.h"
#include "mbframe.h"
#include "mbproto.h"
#include "mbconfig.h"

/* ----------------------- Defines ------------------------------------------*/
#define MB_PDU_FUNC_READ_ADDR_OFF           ( MB_PDU_DATA_OFF )
#define MB_PDU_FUNC_READ_DISCCNT_OFF        ( MB_PDU_DATA_OFF + 2 )
#define MB_PDU_FUNC_READ_SIZE               ( 4 )
#define MB_PDU_FUNC_READ_DISCCNT_MAX        ( 0x07D0 )

/* ----------------------- Static functions ---------------------------------*/
eMBException    prveMBError2Exception(eMBErrorCode eErrorCode);

/* ----------------------- Start implementation -----------------------------*/

#if MB_FUNC_READ_COILS_ENABLED > 0

eMBException
eMBFuncReadDiscreteInputs(UCHAR* pucFrame, USHORT* usLen)
{
	USHORT          usRegAddress;
	USHORT          usDiscreteCnt;
	UCHAR           ucNBytes;
	UCHAR*          pucFrameCur;

	eMBException    eStatus = MB_EX_NONE;
	eMBErrorCode    eRegStatus;

	if(*usLen == (MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN)) {
		usRegAddress = (USHORT)(pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8);
		usRegAddress |= (USHORT)(pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1]);
		usRegAddress++;

		usDiscreteCnt = (USHORT)(pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF] << 8);
		usDiscreteCnt |= (USHORT)(pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF + 1]);

		/* Check if the number of registers to read is valid. If not
		 * return Modbus illegal data value exception.
		 */
		if((usDiscreteCnt >= 1) &&
		        (usDiscreteCnt < MB_PDU_FUNC_READ_DISCCNT_MAX)) {
			/* Set the current PDU data pointer to the beginning. */
			pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
			*usLen = MB_PDU_FUNC_OFF;

			/* First byte contains the function code. */
			*pucFrameCur++ = MB_FUNC_READ_DISCRETE_INPUTS;
			*usLen += 1;

			/* Test if the quantity of coils is a multiple of 8. If not last
			 * byte is only partially field with unused coils set to zero. */
			if((usDiscreteCnt & 0x0007) != 0) {
				ucNBytes = (UCHAR)(usDiscreteCnt / 8 + 1);
			} else {
				ucNBytes = (UCHAR)(usDiscreteCnt / 8);
			}

			*pucFrameCur++ = ucNBytes;
			*usLen += 1;

			eRegStatus =
			    eMBRegDiscreteCB(pucFrameCur, usRegAddress, usDiscreteCnt);

			/* If an error occured convert it into a Modbus exception. */
			if(eRegStatus != MB_ENOERR) {
				eStatus = prveMBError2Exception(eRegStatus);
			} else {
				/* The response contains the function code, the starting address
				 * and the quantity of registers. We reuse the old values in the
				 * buffer because they are still valid. */
				*usLen += ucNBytes;;
			}
		} else {
			eStatus = MB_EX_ILLEGAL_DATA_VALUE;
		}
	} else {
		/* Can't be a valid read coil register request because the length
		 * is incorrect. */
		eStatus = MB_EX_ILLEGAL_DATA_VALUE;
	}

	return eStatus;
}

#endif
